1D age distribution of all disc star particles along with the disc components identified by GMM. The vertical grey lines mark key evolutionary stages of the disc identified by GMM (see Sect. 3.2) from the onset of the thick or high-α disc (10.9 Gyr ago) to the time when the bridge or intermediate-α disc begins to dominate over thick disc (7.7 Gyr ago) and the onset of the α−bimodality (3.6 Gyr ago). The vertical grey bands mark the timing of the bar episode.